Languages develop to fulfill the human needs of communication and, because humans exist for several billion years, nowadays we have a lot of different languages, more or less used.
Some of this languages, such as ancient Greek or Latin, are today spoken very little: this is caused by the rejection of new generations to learn them because of their complexity. Fortunately, Greek and Latin are the basis of many languages, like mediterranean ones, for this even if they die then will continue to live in the countries wet from the mentioned sea.
As I said at beginning, languages exist to permit people to communicate, and if some of them are ending it’s because they are not used and then not more useful. Globalisation and the growing importance of the job market makes English nearly the unique useful language: that’s a risk for other languages. In my opinion reducing it can help to communicate with others but also reduce the cultural heritage of a country and their population: for this it’s not a must to prevent the complete decline of some languages, even if it happens it will mean that its how has to ends.
In conclusion, I think that languages are one of the most important and unique traits of a country, but some of them are naturally destined to disappear because of their disuse. Some languages cannot be saved from this destiny, both because they’re too hard to learn or speak and also for their disuse.